Corrosion Inhibitors

this apparent disadvantage is offset to a large extent by

condition of solution. Such a solution is not suitable for

higher boiling points. Therefore, no cooling problem is

saving and reuse.

g. Conservation of Antifreeze. In the interest of

created by the use of antifreeze solutions for antifreeze

protection in engines designed for water cooling.

conservation, antifreeze solutions-should be drained when

e. Other Properties.

Foaming and leakage

danger of freezing weather is passed and suitable

tendencies, as well as chemical properties of both

solutions should be saved for a second winter's use.

antifreeze compound and water, may affect cooling

Current directives specify that reuse of antifreeze solution

system operation and create maintenance problems.

should be confined to administrative vehicles. Clean

These properties are described in paragraph 2-31b..

solutions only should be saved. Solutions containing rust

will contaminate clean solutions when mixed together in

the same storage container, making the resulting mixture

2-32.

Corrosion Inhibitors

unfit for further use. Reclaimed antifreeze solutions

should always be tested, and fresh antifreeze should be

a. The Corrosion Problem. Water has a natural

added if necessary to increase the freezing protection

tendency to combine chemically with iron and air in the

before such solutions are returned to the cooling system.

system. This chemical action forms rust and may also

As explained in paragraph 2-17b a rust inhibitor must be

cause corrosion damage to metal parts of the system.

added to restore corrosion protection. It is desirable to

Details of the causes and effects of rust and corrosion are

make more frequent inspections of coolant appearance

covered in paragraph 2-16.

when using reclaimed solution, since the effectiveness and

Nature of Corrosion Inhibitors. Protection of the

service lift of the reinhibitor may not equal that of fresh

cooling system against corrosion and rust formation is

solution.

secured by the addition of special materials called

inhibitors to the coolant. Although quantities of materials

2-33.

Coolants

added to provide inhibitor treatment are very small, their

effectiveness in preventing rust and corrosion is very

a. Approved Coolants. The only coolant authorized

great.

Laboratory tests have shown that inhibitor

for ordnance vehicles is antifreeze compound (ethylene-

treatment of water can reduce rusting of iron in the cooling

glycol type).

system by as much as 95 percent.

b. Unapproved Antifreeze.

c. Inhibitor in Antifreeze The proper kind and

Use of unapproved

antifreeze material may cause overheating difficulties and

amount of inhibitor is added to antifreeze compound by the

damage to metal or rubber parts of the cooling system. If

manufacturer. Consequently, there is no need for adding

necessary to use unapproved material in a temporary

an inhibitor to fresh unused antifreeze solution. In fact,

emergency, it should be drained at the earliest possible

nothing but fresh, clean water should be added to new

moment, and cooling system should be thoroughly cleaned

antifreeze when preparing solution.

d. Antifreeze Reinhibitor. The original corrosion

before proper coolant is installed.

c. Use of Engine Cooling System Cleaning

inhibitor in new antifreeze may gradually be weakened and

Compound

finally exhausted by extended use of the solution in the

(1) Engine cooling system cleaning compound MIL-

cooling system. It is therefore necessary to add corrosion

C-10597 will not be used as a routine maintenance

inhibitor compound to antifreeze solutions that are to be

procedure each time antifreeze is added or drained from

used for a second season.

e. Inhibitor for Water. Inhibitor treatment is even

the cooling system. The compound will be used only when

necessary to clean heavily rusted or partially clogged

more necessary when water is used as coolant than during

cooling systems.

the antifreeze season.

Approved material which is

(2) Engine cleaning compound MIL-C-10597 for

provided for adding to water for summer rust prevention is

cooling systems is designed to clean the interiors of

the same as approved reinhibitor for use with used

cooling systems, to neutralize residual cleaning acids, and

antifreeze solutions.

Effect of Operation on Antifreeze Inhibitors.

to coat the interiors with a silicate.

Antifreeze inhibitors may slowly weaken with use and give

less corrosion protection to the system. Contamination of

solution also decreases inhibitor effectiveness and

increase corrosion Complete exhaustion of corrosion

inhibitors is generally indicated by an unusually rusty

2-26